As shown in Patent literature 1, a light irradiation device such as a linear light irradiation device includes: a long LED substrate on which a plurality of LEDs are mounted; and a chassis for housing the LED substrate.
In the light irradiation device, the number of LEDs mounted on the LED substrate, the number of series-connected LEDs is restricted depending on relation between a power source voltage VE and a forward voltage Vf of the LED.
For example, in a case where the power source voltage VE is 24V, the forward voltage Vf of a red LED is approximately 2.2V, and the number of the red LEDs mounted on the LED substrate is 10. In addition, the forward voltage Vf is approximately 3.3V in a case of a white LED, the number of the white LEDs mounted on the LED substrate is 6. Moreover, the forward voltage Vf of an infrared LED is approximately 1.5V, the number of the infrared LEDs mounted on the LED substrate is 15.
However, since the number of the LEDs mounted on the LED substrate varies as described above, a size of the LED substrate varies; accordingly it is required to prepare a dedicated LED substrate for each type of the LED. In addition, the chassis for housing the LED substrate also varies depending on the type of the LED, and accordingly there is a problem that requires the respectively suitable substrates.